xâ(Ï/2-0)æ¶ï¼limf(x)=-1
xâ(Ï/2+0)æ¶ï¼limf(x)=+1
解æï¼
y=|cosx|^(sinx)
(1) xâ(Ï/2-0)æ¶ï¼cosx>0
⇒y=(cosx)^sinx
⇒lny=ln[(cosx)^(sinx)]
⇒lny=sinx*lncosx
⇒(lny)'=(sinx*lncosx)'
⇒
y'/y=cosx*lncosx+sinx*(1/cosx)*(-sinx)
⇒y'/y=cosxln(cosx)-(1/cosx)
⇒
y'=[(cosx)^sinx][cosxln(cosx)-(1/cosx)]
⇒
y'
=(cosx)^(sinx+1)lncosx-(cosx)^(sinx-1)
⇒y'=A-B
xâ(Ï/2-0)æ¶ï¼limA=0ï¼
xâ(Ï/2-0)æ¶ï¼limBæ¯0^0åï¼
åï¼
limlnB
=(sinx-1)lncosx
=lncosx/[1/(sinx-1)]
(å为â/âåï¼ä½¿ç¨
æ´å¿
è¾¾æ³å)
=P'/Q'
(åå
åæ¯åæ¶æ±å¯¼æ°)
=(-sinx)(1/cosx)/{[1/(sinx-1)²]*cosx}
=-sinx*(sinx-1)²
=0
â´ limB=e^0=1
â´ limf(x)=0-1=-1
(2)
åçå¯å¾ï¼
xâ(Ï/2+0)æ¶ï¼limf(x)=0+1=1
PSï¼
éä¸f(x)=|cosx|^sinxçå½æ°å¾
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sorryï¼åè¿°ç¼è¾æç¹çæ¼
xâ(Ï/2-)æ¶ï¼f'(x)=-1ï¼
xâ(Ï/2+)æ¶ï¼f'(x)=+1